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Other Investments - Additional Information (Detail)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2015
USD ($)
Sep. 30, 2015
USD ($)
Dec. 31, 2017
USD ($)
Agreement
Dec. 31, 2015
USD ($)
Dec. 31, 2008
USD ($)
Variable Interest Entity [Line Items]          
Gain from equity method investment       $ 5,000,000  
Great Wall Semiconductor Corporation (GWS) [Member]          
Variable Interest Entity [Line Items]          
Gross investment     $ 4,999,719   $ 0
Gain from equity method investment $ 4,999,719   $ 4,999,719    
Number of supply agreements with GWS | Agreement     2    
Purchase of components under agreement   $ 1,662,000